The present invention relates generally to electronic circuit packaging techniques. More particularly, the present invention relates to electronic circuit package designs that utilize substrate interconnect vias.
Many practical electronic circuit packaging applications, such as those used for optical communication components and wireless communication components, mandate very low signal insertion loss and very low signal return loss characteristics for specific operating frequencies. For example, a number of practical circuit designs (e.g., high speed clock circuits, high speed multiplexer circuits, and the like) may require low signal insertion loss and low signal return loss for a defined operating frequency band or for frequencies up to a specified limit. In this regard, bandpass and lowpass filter designs can be implemented in connection with such circuit designs to ensure that signals at the undesirable frequencies are attenuated while signals at the desired frequencies are efficiently transmitted.
Conventional filtering techniques often utilize special circuit components, e.g., discrete capacitors and inductors, to realize a bandpass filter or a lowpass filter associated with the desired signal. These discrete filtering components require additional space on the substrate, thus resulting in an increased package size, which may not be desirable in many applications. In addition, the use of discrete filtering components increases the complexity and manufacturing cost of the electronic circuit package.
Electronic circuit substrate interconnect arrangements typically employ interconnect vias that establish a conducting pathway between two or more metal layers. The combination of a signal via and at least one reference via allows wave propagation from one layer to another. In lieu of discrete electronic components configured to provide a bandpass or lowpass filter, a multilayer electronic package according to the present invention utilizes the geometry of the signal and reference vias, the number of reference vias, and/or the layout of the conductive signal and reference traces surrounding the signal via to realize the bandpass or lowpass filter.
The above and other aspects of the present invention may be carried out in one form by an electronic interconnect structure that includes a signal via formed within a multilayer substrate having a first metal layer and a second metal layer, and a reference via formed within the multilayer substrate. The signal via and the reference via are configured to propagate a signal from the first metal layer to the second metal layer, and to provide a filter response for the signal.